The present invention relates to a process and an apparatus for applying labels to containers. More particularly, the present invention relates to a process and an apparatus for applying labels to the sidewall of containers having a circular cross-section and a sidewall region which is rounded, or bulbous. The process and apparatus of the present invention are particularly applicable to the labeling of polyethylene terephthalate (PET) beverage bottles.
Applying a label to containers with a bulbous sidewall region, such as the familiar COCA-COLA bottle, is a particularly difficult undertaking. Labels of flexible sheet material can easily conform to a flat surface or a cylindrical surface. But, for such a label to conform to a bulbous surface, it must be gathered, forming wrinkles, or deformed by stretching or shrinking.
In a known technique for applying a label to the bulbous sidewall of a container, the label, of heat shrinkable material, is formed into a sleeve with the overlapping ends secured together. The label sleeve is placed over the container and is then exposed to heat to shrink the label into conformance with the bulbous contour. The manipulation of the label to form the sleeve and then place the sleeve over the bottle requires equipment that is complex and expensive.
In a known technique for wrapping a label about a bulbous sidewall of a container, disclosed in U.S. Pat. No. 5,403,416 (Bright et al.), the leading edge of a heat-shrinkable label is adhesively attached to a narrow area at or adjacent to the maximum diameter of the bulbous region of a bottle. The regions of the leading edge of the label at either side of the adhesive bond are not attached to the bottle sidewall. The label is then wrapped about the bottle, and the trailing end is adhesively attached to the bottle or to an overlapped region of the leading end. The bottle, with the label wrapped in sleeve-like form, then moves past hot air jets to shrink the label into conformance with the bottle contour. A problem with this method is that the adhesive can interfere with the placement of the leading edge of the label on the bottle sidewall, due to the location of the adhesive in coincidence with the maximum diameter region of the bottle. Also, the small size of the adhesive bond between the bottle sidewall and leading edge of the label can compromise the stability of the label as it is subsequently wrapped about the bottle.
Because of the shortcomings of known methods for applying a label to a bulbous sidewall region of a container, a method, and an apparatus, for carrying out the labeling of such containers, which is not hampered by these shortcomings, would be most welcome.